As semiconductor memory devices become more dense, the probability of producing a faulty memory device increases. One chance in a million of producing a faulty memory element is much more risky for 4-Megabit memory device production than it is for 16-kilobit production. One approach to improving memory manufacturing yields is the use of redundant (spare) elements in the memory array. If a memory location is faulty, it can be replaced by redundant memory, thereby making the chip functional.
To replace a memory location, addressing circuits are enabled and disabled by blowing one or more fuses located in the chip. Blowing a combination of fuses replaces a specific memory location.
Memory redundancy fusing ability is not standard in many memory testers, so inexpensive apparatus to assist a tester in this endeavor would be advantageous. Another advantage would be gained if the apparatus allowed a tester to determine the state (blown or intact) of any given fuse of the device under test, for verification or diagnosis. Yet another advantage would be gained if the apparatus was addressable, allowing the tester to blow one or more of a plurality of fuses.